The invention relates to a device and a method for ground freezing.
Methods for freezing earth, known as “ground freezing” are used according to the related art to solidify or stabilise the ground at construction sites. Methods are known that use liquid nitrogen or liquefied air as the refrigerant, for example. Freezing with a brine which is itself cooled by a refrigeration plant is also known. Freezing with liquid nitrogen takes place considerably faster than with brine, due to the low temperature of the liquid nitrogen, although the operating costs (energy costs) in cases of prolonged freezing times with liquid nitrogen are significantly higher than with brine.
In ground freezing methods according to the related art, devices for ground freezing equipped with “freezing lances” are driven into the ground, the freezing lances having an outer pipe and two downpipes arranged in an interior space.
In this context, according to the related art a refrigerant, for example supercooled liquefied gas such as liquid nitrogen is introduced into the interior space through one of the downpipes. Heat is removed from the surrounding earth by the liquid refrigerant, which is in heat conducting connection with the outer pipe, so that the earth surrounding the freezing lance is frozen.
According to the methods of the related art, the exhaust gas (for example gas-phase nitrogen) produced in the interior space by evaporation of the refrigerant is transported to the earth's surface via the second downpipe.
However, a disadvantage of this arrangement is the formation of a substantial cloud on the surface, which can lead in particular to reduced visibility, thus increasing the risk of accidents.
Furthermore, the cold, gas-phase nitrogen exiting the second downpipe at the surface may collect close to the ground, and this can present a suffocation hazard in this area.
It is therefore the object of the present invention to provide a device and method which represent(s) an improvement over the related art in terms of terms of these stated drawbacks.
This object is solved with the device for ground freezing, comprising                a freezing lance which extends along a longitudinal axis and is deigned to be introduced into the earth for the purpose of freezing the ground, wherein the freezing lance includes a pipe mantle that encloses an interior space having a first section for holding a liquid refrigerant, wherein the ground surrounding the freezing lance can be cooled by the refrigerant present in the first section,                    a line protruding into the interior space for supplying the liquid refrigerant in the first section of the interior space,            wherein the device has a first end section, on which a first opening is provided for removing an exhaust gas formed by evaporation of the refrigerant from the interior space,                        
characterized in that
the interior space has a second section adjacent to the first section along the longitudinal axis to hold the exhaust gas, so that the exhaust gas can come into contact with the pipe mantle in the second section,
and a method for ground freezing comprising introducing a freezing lance into a ground, introducing a liquid refrigerant into a first section of the freezing lance, introducing a refrigerant into the first section of the freezing lance wherein the ground is at least partly frozen, forming an exhaust gas from evaporation of the refrigerant in a second section of the freezing lance which adjoins the first section of the freezing lance wherein the exhaust gas is removed from an interior space at a first end section of the freezing lance, and wherein the exhaust gas exchanges heat with a pipe mantle in the second section of the freezing lance such that the exhaust gas is heated by exchange of heat with the ground adjacent to the pipe mantle.
The device has a first device for temperature measurement positioned at a transition area between the first section and the second section, which first device is designed to measure the temperature of the exhaust gas at the transition area between the first section and the second section.
The first device for temperature measurement is displaceable along the longitudinal axis.
The device has a second device for temperature measurement positioned at the first opening, which device is designed to measure the temperature of the exhaust gas at the first opening.
The refrigerant is a supercooled liquefied gas
The supercooled liquefied gas is liquid nitrogen.
A first temperature of the exhaust gas is measured at the transition area between the first section and the second section.
A second temperature of the exhaust gas is measured at the first opening.
An inflow of the refrigerant into the interior space is controlled or regulated by means of the first temperature and/or the second temperature.
A plurality of freezing lances is introduced into the ground, and wherein the first temperature and/or the second temperature is/are only measured at some of the freezing lances.
The refrigerant is stored in a refrigerant container in the event of overpressure, and wherein the refrigerant is introduced into the first section of the interior space from the refrigerant container, and wherein the exhaust gas is drawn out of the interior space through the first opening by a pressure differential between the interior space and an ambient atmosphere around the freezing lance which is in fluid communication with the first opening.